At the moment, Walter Mehring’s poems, essays and novels are out of print in both German and English. Mehring’s The Lost Library:The Autobiography of a Culture is, like Stefan Zweig’s The World of Yesterday, a paean to the humanist culture of Central Europe before the rise of Hitler.
You can read a short bio at Wikipedia and an obituary from the New York Times.
A number of Mehring’s poems were set to music. You can listen to several on YouTube: “Charité”, performed by Wacholder, and “American Riesenspielzeug”, sung by Joseline Gassen.